Carbon monoxide reactive separation with basic 1-hexyl-3-methylimidazolium chlorocuprate(I) ionic liquid: Electrochemical determination of mass transport properties

The design of novel room temperature ionic liquid-based (RTIL) processes for gas separation relies on the correct knowledge of the mass transport properties. In the present study, the diffusivity and mass transfer coefficient of copper(I) ions in the ionic liquid 1-hexyl-3-methylimidazolium chlorocuprate are characterised since this knowledge is of great significance for the development of carbon monoxide reactive separation processes based on the selective and reversible reaction between this gas and the copper(I)-based RTIL. The diffusion coefficients were obtained from the reduction of copper(I) ions present in a 100 mmol copper(I) L−1 solution by chronopotentiometry (CP) and linear sweep voltammetry with rotating disk electrode (RDE) techniques. The diffusion coefficients obtained with CP are in the range 2.9 × 10−9-7.76 × 10−9 cm2 s−1 for temperatures between 293 and 313 K. The effect of temperature on the diffusion coefficients is well-described by an Arrhenius-type behaviour with an activation energy of 37.0 kJ mol−1. Mass transfer coefficients were determined by the linear sweep voltammetry method. Values obtained varied between 1.3 × 10−6 and 7.8 × 10−6 cm s−1 in the temperature range 283-333 K.